Solution: This is a relational change to the formula. If you increase the temperature of a black body by a factor of 5, how does its value of max change? Basically as the temperature goes up, max goes up and vice versa.ġ. The constant in the formula shows how these two things are related, and could be different if you measured the wavelength or temperature in different units. T = temperature of the object, in degrees Kelvin (K).max = wavelength where most of the light is emitted, measured in meters.This law is used to explain why the colors of objects change as you change their temperatures. Wien's Law - This law is used for black bodies, perfect radiation (light) emitters and absorbers and indicates at which wavelength they tend to give off most of their light. You are basically multiplying the right side by 25 when you change the wavelength, so the result is the same, the energy is 25 times greater. Looking at the first version of this formula. If the wavelength is 25 times smaller than the frequency is 25 times larger. You could also figure this out by looking at how the frequency changes when you change the wavelength. Solution: Look at the second version of the formula -īy changing the wavelength, you are dividing the bottom by a factor of 25, or written mathematicallyīut when you divide by a fraction that is the same as multiplying by its reciprocal, so the end result is If a light sources wavelength is 25 times smaller than before how does that change the energy of the photons? The only thing that can change on the right side is the frequency (f), which becomes 30 times larger, therefore theĢ. Solution: Look at this version of the formula. If you increase the frequency of a light source by a factor of 30, how much does the energy of the photons change? = wavelength of the light, usually in units of metersġ.h = same constant as before, still ugly.The result is how the energy depends upon the wavelength of light. The second version of the formula is found by using the light properties formula (c = f) and substituting that in for the above relation. f = frequency of the light in units of per seconds (1/seconds).h = Constant, actually known as Planck's constant, a really ugly number.In general, only relational values will be needed (no exact values calculated). This formula is for the energy of an individual photon. So as wavelength goes up frequency and energy go down. The basic upshot is that as frequency goes up, so does energy, however wavelength goes down. Solution: Rearrange the formula to solve for wavelength -Īnd put in the various values, no conversions are needed, though you need to write frequency properly -Įnergy of a photon - There are two versions of this formula, one using the frequency, the other using the wavelength. If a particular type of light has a frequency of 1 million /second, what is its wavelength? If a particular type of light has a wavelength of 6430 Å, what is its frequency? Mathematically this would be written asĪnd the 10s cancel out. So for the left side to stay the same while becomes 10 times larger, f must become 10 times smaller. Solution: Since the speed of light (c) cant change, when you change one part of the formula, the other part mush If a light's wavelength is increased by a factor of 10, how does its frequency change? So if the wavelength goes down the frequency goes up, and vice versa.ġ. That means if you change something on the right side (either the wavelength or the frequency) then the other thing has to also change, but in the opposite sense. So the left side of the formula always has the same value. This is a very important relationship since it tells you several things - first of all, the speed of light is constant - it never changes (as far as we're concerned in this class). f = the frequency at which light waves pass by, measured in units of per seconds (1/s).= the wavelength of light, usually measured in meters or Ångströms (1 Å = 10 -10 m).c = the speed of light = 300,000 km/s or 3.0 x 10 8 m/s.A fairly simple, but important relationship. Light Properties - shows the relationship between the speed of light, its wavelength and its frequency.